A solid electrolytic capacitor has been known as a capacitor suitable for size reduction, and a solid electrolytic capacitor having a solid electrolyte layer made of a conductive polymer has been widely used. For the solid electrolytic capacitor, studies on improving restoration capability in a dielectric film have been conducted by adding an ionic liquid to a solid electrolyte (see, for example, International Publication No. WO 2005/012599, Unexamined Japanese Patent Publication No. 2006-24708, Unexamined Japanese Patent Publication No. 2008-16835, and Unexamined Japanese Patent Publication No. 2008-283136). Here, the ionic liquid is a salt that is melted and kept in a liquid state under an ordinary-temperature environment. The ionic liquid has properties such as non-volatility or high ionic conductivity.